William Castle was losing touch with his audience around this time and the cheap and efficient producer side of him was clearly winning over the carny style director side of him.The concept of a black comedy geared for kids was a bit novel but Pat Cardi is just too annoying as the little boy and some of the plot devices and effects are real eyeball rollers even for a vintage Castle movie.Nigel Green clearly knows what he's doing and refuses to play down to the material.It may seem like he's going over the top at times but his character is supposed to enjoy outwitting and doing away with the boy that stands in the way of his inheritance.As others have stated the scenes with the shark in the pool are pure hokum guaranteed to illicit peals of laughter as they shift from one scene of a rubbery fin by the diving board to an old and grainy shot of a shark in the ocean.The basic concept of who's killing who? Child or adult? could be remade quite effectively today but this is largely a flop, Stick with The TIngler Or House On Haunted Hill.
Review of Let's Kill Uncle
